Most privacy policies are in legalese, and hard experience has shown that what I, as a non-lawyer, think they say is quite often very different from what they actually say.

As a result, I gave up bothering to read them unless they're one or two paragraphs long. I simply assume they say what 90% of them really say: they can take any data they like, do whatever they like with it, and they can unilaterally change the agreement any time they want.